package leetcode;

/**
 * 200. 岛屿数量
 * 给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。
 * 岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。
 * 此外，你可以假设该网格的四条边均被水包围。
 * 示例 1：
 * 输入：grid = [
 * ["1","1","1","1","0"],
 * ["1","1","0","1","0"],
 * ["1","1","0","0","0"],
 * ["0","0","0","0","0"]
 * ]
 * 输出：1
 * 示例 2：
 * 输入：grid = [
 * ["1","1","0","0","0"],
 * ["1","1","0","0","0"],
 * ["0","0","1","0","0"],
 * ["0","0","0","1","1"]
 * ]
 * 输出：3
 * 提示：
 * m == grid.length
 * n == grid[i].length
 * 1 <= m, n <= 300
 * grid[i][j] 的值为 '0' 或 '1'
 */

public class problems_200 {

    public static void main(String[] arge) {
        char[][] grid = new char[][]{
                {'1', '1', '1', '1', '0'},
                {'1', '1', '0', '1', '0'},
                {'1', '1', '0', '0', '0'},
                {'0', '0', '0', '0', '0'}
        };
        System.out.println(new Solution().numIslands(grid));
    }

    static class Solution {
        public int numIslands(char[][] grid) {
            // 初始化
            int num = 0;
            for (int i = 0; i < grid.length; i++) {
                for (int j = 0; j < grid[i].length; j++) {
                    // 棋盘遍历
                    // 找到陆地点的时候
                    if ('1' == grid[i][j]) {
                        num++;
                        fillPoint(grid, i, j, (char) ('a' + num));
                    }
                }
            }
            return num;
        }

        // 节点填充
        private void fillPoint(char[][] grid, int x, int y, char val) {
            if (x < 0 || x >= grid.length) return;
            if (y < 0 || y >= grid[x].length) return;
            if ('1' == grid[x][y]) {
                grid[x][y] = val;
                fillPoint(grid, x + 1, y , val);
                fillPoint(grid, x - 1, y , val);
                fillPoint(grid, x, y + 1 , val);
                fillPoint(grid, x, y - 1 , val);
            }
        }
    }
}
